Electric hammer.



PATENTED 001 25, 1904.

A. F. CHRISTMAS.

ELECTRIC HAMMER.

APPLIOATIOIT FILED DBO. 2. 1903.

no MODEL.

WE TNESSEZ$.

UNITED STATES Patented October 25, 1904.

PATENT OFFICE.

ADOLPH F. CHRISTMAS, OF PITTSBURG, PENNSYLVANIA, ASSIGNOR OF TWVO-THIRDSTO FRANK R. MGFEATTERS, OF VVILKINSBURG, PENN- SYLVANIA.

A ELECTRIC HAMMER.

SPECIFICATION forming part of Letters Patent N0. 773,122, dated October25, 1904:. Application filed December 2, 1903. Serial No. 183,620. (Nomodel.)

To all whom, it may concern.-

Be it known that I, ADoL'rI-I F. CHRISTMAS, a resident of Pittsburg, inthe county of Allegheny and State of Pennsylvania, have invented a newand useful Improvementin Electric Hammers; and I do hereby declare thefollowing to be a full, clear, and exact description thereof.

My invention relates toelectric reciprocating tools-such as hammers,chipping-tools, drills, calking tools, and the like; and the object isto provide a tool of thischaracter which will give a strong blow and yetis simple in its .construction, and which can be started by the mere actof grasping the tool firmly to press it against the work and stopped bymerely releasing the firm grasp on the tool.

In the accompanying drawings,Figure 1 is a longitudinal section througha hammer constructed according to my invention. Fig. 2 is across-section on the line 2 2, Fig. 1; and Fig.3 is a longitudinalsection showing a modification.

My hammer is provided with two coils 1 and 2, having within them thelining tube or bobbin 3, in which reciprocates the core or armature 4.The coil and armature are inclosed in a suitable casing, and as tools ofthis character are subjected to violent shocks difiiculty has heretoforebeen experienced in so constructing the casing as to withstand theseshocks. My casing comprises the front end or nose-piece 5, preferablyformed of soft steel, having an opening 6 therethrough for the passageof the shank of the tool. A hardenedsteel bushing 7 is placed in thisend piece to take the wear of the tool-shank. This nosepiece is providedwith an external shoulder 8, which is engaged by an internal shoulder 9on the coil-inclosing tube 10. Preferably both the shoulders 8 and 9 areslightly undercut, as shown, so as to prevent their slipping past eachother after being worn. The inclosing tube 10 at its opposite end isprovided with an external annular shoulder 11, which is engaged by aninternal shoulder 12 on one end of a coupling-sleeve 13, which at itsopposite end is internally threaded and engages threads on the inner endof a handle-piece 1A. The coupling-sleeve binds all the parts together.

The'inner end of the sleeve or bobbin 3 is tightly closed by means of a.head 16, which is held in place by the handle-piece bearing against thesame. Preferably there will be interposed between this head and the core45 some means for cushioning said core and starting it on its returnmovement. This means may be a helical spring 17, as is shown in Fig. 3,which will cushion the core 4: as it approaches the head 16 and startson its return movement. Preferably, however, this result will be gottenby makingthe core I to closely fit the bore of the sleeve 3, and as aconsequence the inner end of said sleeve will act as a pneumaticcylinderthat is to say, when the core 4: is drawn toward the head 16 bythe energization of the coil 2 the air between said core and the head 16will become compressed, thus acting as a cushion and also serving by-itsexpansive force to start the core 4 on its return movement. The coils 1and 2 of the hammer will be alternately energized, and each one for onlya small interval of time, the coil 2 serving to draw the core backtoward the head 16 and the coil 1 serving to draw said core in theopposite direction to give the blow, being aided in this by theexpansive power of the air which has been compressed between the core 4and the head 16, thus getting a powerful blow. In order that thedash-pot may not act by suction to retard the core Lwhen it approachesthelimit of its outward movement, an air inlet or inlets'are providedleading into the sleeve 3 in such position that they will be uncoveredby the inner end of the core 4 passing beyond the same when the latterapproaches the limit of its outward movement. These air-inlets may beprovided in any suitable way; but, as shown in the drawings, a duct orducts 18 are formed in the soft-steel partition 19, which divides thetwo coils, this duct communicating with a groove 20, formed in the innerface of the sleeve 3 and terminating at such a point that its inner endwill be uncovered by the inner end of the core 4 when the latterapproaches the limit of its outward movement. The outer end of thesleeve 3 is in free communication with the atmosphere, as by means of aduct 21, extending through the ICU nose-piece 5, thus preventing acushion being formed in front of the core.

The handle-piece 1% is provided with the usual member 23 to be graspedby the hand of the operator. This handle portion ismade hollow, and init are mounted the terminals 2 1 and also a switch-blade 25, which ispivoted at 26 and provided with a projection or arm 27. To the latter isconnected one end of a helical spring 28, the opposite end of which isconnected to the handle at 29, being so arranged that the axis of saidspring will pass the pivot-center 26 in the movement of the switch-bladein both directions, thus causing the same to move with a snap andinterrupt any arcs that maybe formed. Also pivoted in the handle is aswitch-closing lever 30, which is provided with aforked portion 31,engaging the projection 27 of the switchblade, said lever being sopositioned with reference to the portion 23 of the handle that when thehandle is firmly grasped, as it must be in pressing the tool a ainst thework. it

will move the switch-blade to close the same. A flat leaf-spring32presses against the lever 30, so as to move the same to open theswitchblade as soon as the grasp on the tool-handle is released. In thismanner I provide for the starting and stopping of the tool without theoperator having to give any especial attention thereto, it beingaccomplished by the mere act of properly using the tool.

In connecting the tool the wires lead through an opening 33 into thechamber in thehollow handle and are connected to the terminals and haveportions 34L thereof extending to the coils through holes in the innerweb member 35 of the handle and the head 16. In order that the handleweb member 35 will not shear off the circuit-wires, it is necessary toprevent the rotation of the handle with reference to the head 16. Thisis conveniently accomplished by having a key 35 projecting into aliningopenings in the head 16 and the handle member.

The wiring of this hammer will be such that independent wires lead tothe coils 1 and 2, and in connection therewith suitable means will beprovided for directing the current alternately to said coils, andpreferably the arrangement will be such as to energize each of the coilsfor only a short interval of time, this preventing the heating of thetool, as would result by continuing the current, but at the same timegetting a sufliciently strong magnetic pull on the core. Thiscircuit-interrupting device preferably will operate in synchronism withthe period of oscillation of the core a, as more specifically describedand claimed in my application, Serial No. 183,518, filed December 2,1903.

'hat I claim is- 1. In an electric reciprocating tool, the combinationof a sleeve or bobbin closed at one end, a coil thereon, a reciprocatingcore in said sleeve and closely fitting the same, and

* an air-duct leading into said sleeve and so arranged that it willremain closed until the core approaches the limit of its outwardmovement.

2. In an electricreciprocating tool, the combination of a sleeve orbobbin closed at one end, two coils thereon, a partition separating thesame, a reciprocating core in said sleeve and closely litting the same,and an air-duct through the said partition and entering said sleeve atsuch a point that it will be uncovered when the core approaches thelimit of its outward movement.

3. In an electric reciprocating tool,the combination of a casing, a coiland a core therein, ahandle for said tool. a circuit-closer, andoperating means for the circuit-closer on said handle and in suchposition that the act of grasping the handle closes the circuit.

4:. In an electric reciprocating tool,the combination with the casing,of a coil and core therein, a handle for said tool, a circuit-closer,operating means for said circuit-closer mounted on said handle and soarranged that the act of grasping the handle closes the circuit, and aspring for normally holding the circuitcloser open.

5. In an electric reciprocating tool,the combination with the casing, ofa coil and core therein, a handle for said tool, a circuit-closerpivoted in said handle, a helical spring having one end connected tosaid circuit-closer and its opposite end connected to the handle andarranged so as to pass the pivot-center of the circuit-closer in bothIUOVOI'YlOllllS of the latter, and operating means for saidcircuitcloser mounted in the handle and so arranged that the act ofgrasping the handle will close the circuit.

6. In an electric reciprocating tool,the combination with the casing, ofa coil and core therein, a handle for said tool, a circuit-closerpivotally mounted in said handle, an operating-lever also pivotallymounted in the handle and arranged to engage the circuit-closer andbeing in such position that the act of grasping the handle will closethe circuit, and a spring bearing against said operating-lever andnormally holding the circuit-closei' open.

7. In a reciprocating electric tool, the combination with the casing, ofa coil and core therein, a handle for said tool, a circuit-closerpivotally mounted in said handle, an operating-lever therefor alsopivotally mounted in the handle and arranged so that the act of graspingthe handle will operate the same,

and a fork on said lever engaging a pro ection on the circuit-closer.

In testimony whereof I, the said ApoLmI I CHRIS'LMAS, have hereunto setmy hand.

ADOLPH F. (JIIRISIAIAS. Witnesses:

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